Bipolar ESD protection structure

ABSTRACT

The invention describes the fabrication and structure of an ESD protection device for integrated circuit semiconductor devices with improved ESD protection and resiliency. A vertical bipolar npn transistor forms the basis of the protection device. To handle the large current requirements of an ESD incident, the bipolar transistor has multiple base and emitter elements formed in an npn bipolar array. To assure turn-on of the multiple elements of the array the emitter fingers are continuously or contiguously connected with an unique emitter design layout. The contiguous emitter design provides an improved electrical emitter connection for the device, minimizing any unbalance that can potentially occur when using separate emitter fingers and improving the ability for the simultaneous turn on of the multiple emitter-base elements. The emitter is contained within the footprint of the collector elements, and enables containment of device size, therefore minimizing device capacitance characteristics important in high speed circuit design. Other embodiments of the invention use variations in the structure of the common contiguous emitter conductor as well as different base conductor structure layouts.

(1) FIELD OF THE INVENTION

[0001] The present invention relates generally to the fabrication andstructure of a semiconductor device for ESD protection of electroniccircuit devices and more particularly to a continuous emitter bipolardevice with improved ESD circuit protection characteristics.

(2) DESCRIPTION OF PRIOR ART

[0002] Because of high input impedance and thin oxide gate structures,the problem of Electrostatic Discharge (ESD) damage with field effecttransistor (FET) devices can be severe. Therefore the input/output (I/O)circuit locations or pads usually have a protective device connectedbetween the I/O pad and the internal circuits as shown in FIG. 3 whichallows the ESD current to be shunted to ground. Another importantcharacteristic of the ESD protection device is that it must notinterfere with the operation of the devices it is designed to protect,while at the same time providing good protection when abnormal or ESDvoltage incidents occur. Typical ESD protection devices consist of a nchannel metal oxide semiconductor (NMOS) with an associated lateralparasitic npn bipolar transistor. Once triggered by an ESD incident, thedevice operates in the lateral npn mode to pass the high current.However, a vertical bipolar npn structure has better power dissipationcapability than the NMOS, and is frequently used to provide ESDprotection for the internal circuits.

[0003] ESD efficiency is typically measured by dividing the ESD“threshold” voltage by the area of the ESD protection device asdescribed in the report by Chen et al., “Design and Layout of High ESDPerformance NPN Structure for Submicron BiCMOS/Bipolar Circuits.”, IIIEJournal, 1996 0-7803-2753-5/96, pp. 227 to 232. ESD threshold can becorrelated to the secondary breakdown characteristic of the bipolartransistor as depicted in FIG. 1. The initial collector base breakdown(Bvcbo) initiates the device turn on which is followed by breakdown ofcollector to emitter (BVceo) as conduction enters the avalanche regionbetween BVceo and Vt2, It2. Vt2 and It2 define the beginning of thesecondary breakdown region in which the npn can be damaged due to Jouleheating of the collector base junction. The higher the It2, that is thecurrent threshold prior to secondary breakdown, the higher the ESDthreshold, the better the ESD characteristics of the device. It is foundthat an increase in It2 and hence ESD threshold, scales with emitterlength. However, as emitter length is increased there is a correspondingincrease in device area. This takes up valuable active circuit area, andresults in increased device capacitance which is detrimental in highspeed circuit operation. In an effort to control or reduce ESD devicearea while maintaining or improving ESD efficiency, prior art designshave used multiple emitter finger designs. The top view horizontallayout of one such design is depicted in FIG. 4. It is seen in FIG. 4that there are N+1 base conductors 20 for every N emitter fingers 28. Inthe case shown, N=4 and therefore there are 5 base connections 20running in a horizontal interdigitated fashion between the emitterfingers 28.

[0004] The schematic of FIG. 3 shows a simplified equivalent circuit ofthe device with the collectors 18 electrically tied together 34 and tothe input pad 40. The bases 20 are tied to the emitters 28 through thebase spreading resistance 38 depicted as resistors Rb1, Rb2, Rb3, andRb4 and additional conductor elements 32. Typically the base and emitterelements are then connected to ground 30. The objective of the prior artlayout is to optimize the design to make the base resistance as equal aspossible (Rb1=Rb2=Rb3=Rb4) so that the emitters will turn on uniformlyat the same time to conduct the ESD current. However, there are stillfour different emitter fingers 28 in FIG. 4 in which process variationcan cause slight differences in electrical characteristics as well as inthe characteristics of the base elements. This design structuretherefore cannot always assure turn-on of all the emitter base elementsto maximize the device ESD current capability.

[0005] It is desired to find a manufacturing method and device structurethat maintains or improves the ESD efficiency of the multi emitterfinger device with improved turn on characteristics and resistance toESD damage.

[0006] U.S. Pat. No. 5,850,095 issued to Chen et al., describes anelectrostatic discharge (ESD) protection circuit with a differentemitter layout and structure from that described by the invention

[0007] U.S. Pat. No. 5,341,005 issued to Canclini shows differentstructures for ESD protection.

[0008] U.S. Pat. No. 5,528,189 issued to Khatibzadeh., shows anamplifier with ESD protection with emitter finger layouts.

[0009] The following technical report previously referenced also refersto the subject of ESD protection.

[0010] “Design and Layout of High ESD Performance Circuits, IEEE, 19960-78032753-5/96 pp. 227 to 232. The report discusses various ESDprotection device layouts.

SUMMARY OF THE INVENTION

[0011] Accordingly, it is the primary objective of the invention toprovide an effective and manufacturable method and structure forimproving semiconductor device resistance to the potential damage causedby the phenomenon known as electrostatic discharge (ESD) by utilizing avertical bipolar npn transistor structure.

[0012] It is a further objective of the invention to improve ESDprotection by providing a structure with higher ESD efficiency and beless susceptible to ESD damage.

[0013] Yet another objective of the invention is to provide a structurewith improved ESD efficiency while at the same time maintaining orreducing structure size and capacitance which will enable reduced chipsize and improved high speed performance.

[0014] A still additional objective of the invention is to provide theimproved ESD protection without changing the characteristics of theinternal circuits being protected and by using a process compatible withthe process of integrated MOS device manufacturing.

[0015] The above objectives are achieved in accordance with the methodsand structures of the invention which describes an ESD protection devicefor integrated circuit semiconductor devices with improved ESDprotection and resiliency and a manufacturing method for the device. Avertical bipolar npn transistor forms the basis of the protectiondevice. To handle the large current requirements of an ESD incident, thebipolar transistor has multiple base and emitter elements formed in anpn bipolar array. To assure turn-on of the multiple elements of thearray the emitter fingers are continuously or contiguously connectedwith a unique emitter design layout structure. The contiguous emitterdesign provides an improved electrical emitter connection for thedevice, minimizing any unbalance that can potentially occur when usingseparate emitter fingers and improving the ability for the simultaneousturn on of the multiple emitter-base elements. The emitter is containedwithin the footprint of the collector elements, and enables containmentof device size, therefore minimizing device capacitance characteristicsimportant in high speed circuit design. Other embodiments of theinvention use variations on the structure of the common contiguousemitter conductor as well as different base conductor structure layouts.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 represents the typical current (I) vs. voltage (Y)characteristic for the vertical npn bipolar transistor with initialturn-on (Bvcbo), avalanche region (BVceo to Vt2, It2,) and secondarybreakdown region beyond Vt2, It2.

[0017]FIG. 2 is a cross section of a multi finger npn bipolar transistorstructure.

[0018]FIG. 3 shows a simplified equivalent circuit diagram of a multifinger bipolar ESD protection device with base and emitter elements tiedto ground and collector connected to the chip integrated circuit inputpad.

[0019]FIG. 4 is a top view of the horizontal layout of the prior artmultifinger npn bipolar ESD protection device with the number of emitterfingers=4, and the number of base elements=5.

[0020]FIG. 5A through 5D are top views of the horizontal layouts ortopography of different embodiments of the invention bipolar ESDprotection device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021]FIG. 2 depicts a vertical cross section of a multiple elementbipolar ESD protection device. The starting structure is a p dopedsubstrate 10, typically created on a silicon wafer of 100 crystalorientation and with a doping level in the range of 10¹⁵ atoms per cubiccentimeter (a/cm³). A heavily doped n+ first semiconductor layer 12called a buried layer or subcollector is formed upon the substratetypically using arsenic or antimony as impurity dopents and using eithera chemical diffusion or an ion implant process. An ion implant processtypically uses an implant energy in the range of 30 KeV with a dosage of10¹⁵ atoms per square centimeter (a/cm²) to produce a n+ buried layerdoping level between 10¹⁸ and 10¹⁹ a/cm³. Next, a light to moderatelydoped n type epitaxial second semiconductor layer 14 is deposited with adoping level typically in the range of 10¹⁵ to 10¹⁶ a/cm³ with arsenicfrequently being used as the dopent source element. A plurality of deepn+ regions 16 are implanted into the second semiconductor layer 14beneath the collector contact regions typically using either an arsenic,antimony or phosphorous dopent with an implant energy in the range of 30KeV with a dosage of 10¹⁵ a/cm² to produce an n+ buried layer dopinglevel between 10¹⁸ and 10¹⁹ a/cm³. This provides a low resistance pathto the surface conductor system 34 for the collector current. Thestructure processing is continued by implanting a third semiconductorlayer 24 of p dopent, usually boron, with an implant energy in the rangeof 30 KeV with a dosage of 10¹⁴ a/cm² to produce a p layer with atypical impurity concentration in a range of between 10¹⁷ and 10¹⁸ a/cm³to form the transistor base regions. This is followed by implanting aplurality of p+ regions 22 using boron as a source with doping levelstypically between 10¹⁸ and 10¹⁹ a/cm³ within the third semiconductorlayer base region 24 to form high conductivity regions for the baseelectrical contacts 20. Next, a plurality of third n doped semiconductorregions is implanted, typically with phosphorous, with an implant energyin the range of 30 KeV and with a dosage of between 10¹⁶ and 10¹⁷ a/cm²to produce a p layer with a typical impurity concentration in a range ofbetween 10¹⁹ and 10²⁰ a/cm³ for the transistor emitter regions 26. Theelectrical contacts with the surface conductors for the collector 18,base 20, and emitter 28 are typically made by using a refractory metalsilicide such as titanium silicide (TiSi₂) or tungsten silicide (Wsi₂)together with doped polysilicon (poly) or aluminum conductor elements.

[0022] A simplified electrical schematic of the ESD device is depictedin FIG. 3. The emitters 28 are normally connected together through aconductor system 30 and to a second voltage source, typically ground.The base contacts 20 are normally connected together through a baseconductor system 32 and to the emitter conductor system 28 and then toground 30. The base resistance 38 (Rb1, Rb2, Rb3, Rb4 for the structuredepicted) represent the base spreading resistance, the electricalresistance of the conducting area of the base regions. It is the smalldifferences in the base resistance's as well as the slight differencesin the emitter contact resistance's and other device parameters such asgain that tend to prevent complete turn on of all the multi-fingeremitter-base element in prior art designs.

[0023] The top horizontal topography of the prior art configuration isshown in FIG. 4. The example shown is for a N emitter element 28 bipolartransistor with N equal to 4. The figure shows four horizontalindividual emitter fingers 28 on the top surface together with N+1 orfive horizontal interdigitated base fingers 20 and two horizontalcollector fingers 18. The final electrical connections whereby thecollectors are tied together and to an input pad and the emitters andbase elements are tied together and connected to a second voltagesource, typically ground, are not shown in this top horizontal view ofthe device layout. In this prior art layout great care must be exercisedin the design and processing in order to have all the electricalparameters such as base resistance match as closely as possible in orderto have as many emitter fingers 28 as possible turn on simultaneously.

[0024]FIG. 5A shows a top view horizontal layout of one embodiment ofthis invention with N, the number of emitter regions again being equalto four. These emitter regions 26 in FIG. 2 are connected together withvertical conductors on alternate ends of the emitter horizontalconductor stripes to form a continuous serpentine emitter 28A. The baseconductors 20A are interdigitated on each side of the serpentine emitter28A with N+1 elements or 5 for the case shown. The collector electricalcontact conductors 18A are two horizontal conductors, one at the top andone at the bottom of the device. Not shown in FIG. 5A are the additionalcollector electrical connections shown in FIG. 3 which connect thecollectors 34 together and to a first voltage source, the I/O pad 40,and the conductor 32 which connects the serpentine emitter 28A to thebase conductor elements 20A and to the second voltage source, ground 30.The continuous serpentine emitter conductor 28A provides the capabilityof a single emitter current which provides a high assurance that all thebase elements will conduct minimizing the possibility of localizeddevice damage caused by excessive current, and therefore excessive jouleheating, in any one transistor element. This provides good ESDprotection while at the same time minimizing the device area.

[0025] Another embodiment of the invention is shown in FIG. 5B. Theserpentine emitter 28B is connected with vertical conductors atalternate sides of the horizontal emitter fingers the same as previouslyshown. However, the interdigitated base fingers 20A shown in FIG. 5A areremoved leaving only two horizontal base fingers 20B on the top andbottom of the configuration between the top and bottom horizontalcollector conductor stripes 1 8B and the continuous serpentine emitterconductor 28B. This improves semiconductor action which otherwise mightbe impaired by having too many base elements within the emitter regions.

[0026] Again not shown in FIG. 5B are the additional collectorelectrical connections shown in FIG. 3 which connect the collectors 34together and to a first voltage source, the I/O pad 40. Also not shownis the conductor 32 which connects the serpentine emitter 28B to thebase conductor elements 20B and to the second voltage source, ground 30.

[0027] Yet another embodiment is shown in the top horizontal layout viewdepicted in FIG. 5C where the emitter has the horizontal emitter fingers28C being connected at one end, the right end depicted in the figureFIG. 5C, forming a contiguous connection with a fork or comb likearrangement. Again, the base fingers 20C appear as horizontal contactconductors at the top and bottom of the layout between the horizontaltop and bottom collector contact conductors 18C and the contiguousemitter contact conductor 28C. This shows the flexibility of thecontiguous emitter conductor design layout. As an alternative, theemitter vertical conduction paths could be connected on the left side ofthe horizontal emitter finger array.

[0028] Again not shown in FIG. 5C are the additional collectorelectrical connections shown in FIG. 3 which connect the collectors 34together and to a first voltage source, the I/O pad 40. Also not shownis the conductor 32 which connects the serpentine emitter 28C to thebase conductor elements 20C and to the second voltage source, ground 30.

[0029]FIG. 5D shows yet another embodiment of the invention with thehorizontal emitter finger contact conductors 28D being connected on bothends of the structure forming a border or box shape with grids. Onceagain, the base has two horizontal finger contact conductors 20D at thetop and bottom of the structure between the horizontal top and bottomcollector contact conductors 18D and the continuous emitter contactconductor 28D. This embodiment shows the flexibility of the contiguousemitter conductor design. In this case, more contact area is availableto handle higher ESD currents if required. The invention provides thecapability to have design tradeoffs between greater contact/conductorarea for high current handling with minimum resistance encountered, andpossibly less area with less capacitance for higher performance. Again,the final electrical conductor system connecting the emitters and baseelements to ground and the collector to the input pad are not shown inFIG. 5D.

[0030] While the invention has been particularly shown and describedwith reference to the preferred embodiments thereof, it will beunderstood by those skilled in the art that various changes in form anddetails may be made without departing from the spirit and scope of theinvention.

What is claimed is:
 1. An integrated multiple transistor ESD protectionstructure on a semiconductor substrate, functionally connected to anintegrated circuit input or output pin which will prevent electrostaticdischarge damage to said integrated circuit comprising; a firstsemiconductor layer having a first conductivity dopent type; a secondsemiconductor layer overlying said first semiconductor layer, having asimilar conductivity type as said first layer, but a different dopentconcentration; a third semiconductor layer having a second conductivitydopent type opposite that of said first semiconductor layer, disposed inoverlying relation to said second semiconductor layer; a plurality offirst regions of said first conductivity type electrically connectingwith said first semiconductor layer, having a top element makingelectrical contact to said first regions and said first semiconductorlayer; a plurality of second regions of said second conductivity dopenttype laterally spaced from said first regions, being electricallyconnected to said third semiconductor layer having a top element makingelectrical contact to said second regions and said second semiconductorlayer; a plurality of third regions of said first semiconductor layerconductivity dopent type laterally spaced and interposed between saidsecond regions;
 2. The ESD protection structure of claim 1 whereby theplurality of first regions together with the associated connected firstsemiconductor layer are with n dopent and form multiple collectorelements of a bipolar transistor in which the bases are formed by saidthird conductivity layer and associated said plurality of second regionsof p dopent, and by which multiple emitter elements are formed by saidplurality of laterally spaced third regions of n type dopent.
 3. The ESDprotection structure of claim 1 whereby the protection structure is abipolar npn transistor.
 4. The ESD protection structure of claim 1whereby said first collector regions have horizontal contact conductorstripes at the top and bottom of said transistor array which areultimately connected together and to a first voltage source of saidintegrated circuit input/output pin.
 5. The ESD protection structure ofclaim 1 whereby said laterally spaced pluralities of third emitterregions are arranged in an alternating array within said thirdsemiconductor base layer, with “N” number of emitter regions whereby “N”corresponds to the number of multiple bipolar transistors in anelectrically parallel transistor array that comprise said ESD protectionstructure.
 6. The ESD protection structure of claim 1 whereby said thirdsemiconductor emitter regions are electrically connected by a contactconductor element with N horizontal conductor stripe elements andfurther connected in a contiguous serpentine manner by vertical contactconductor elements at alternate ends of said horizontal emitter stripes,and said base has horizontal contact regions interdigitated between saidhorizontal emitter stripes with the number of interdigitated horizontalbase elements being equal to N+1.
 7. The ESD protection structure ofclaim 1 whereby said third semiconductor emitter regions areelectrically connected by a contact conductor element with N horizontalconductor stripe elements and further connected in a contiguousserpentine manner by vertical contact conductor elements at alternateends of said horizontal emitter stripes.
 8. The ESD protection structureof claim 1 whereby one said p+ doped second semiconductor basehorizontal contact region lies between said top horizontal collectorcontact and said multiple emitter contact regions, and a second said p+doped semiconductor base horizontal contact region lies between thebottom horizontal collector contact and said multiple emitter contactregions enabling surface connections to said base regions
 9. The ESDprotection structure of claim 1 whereby said third semiconductor emitterregions are electrically connected by a conductor element with Nhorizontal stripe conductor elements and connected in a contiguous comblike manner by a vertical contact conductor element at one end of saidhorizontal emitter conductor stripes.
 10. The ESD protection structureof claim 2 whereby said third semiconductor emitter regions areelectrically connected by a contiguous contact conductor element with Nhorizontal stripe conductor elements and connected in a contiguous boxlike manner by vertical contact conductor elements at both ends of saidhorizontal emitter conductor stripes.
 11. The ESD protection structureof claim 1 whereby said plurality of second semiconductor base regionelectrical contact conductors and said third semiconductor emitterregion electrical contact conductors are ultimately connected togetherand to a second voltage source, typically ground.
 12. An integratedmultiple vertical npn transistor ESD protection structure on asemiconductor substrate, functionally connected between an integratedcircuit input or output pin and ground which will prevent electrostaticdischarge damage to said integrated circuit comprising; a firstsemiconductor layer having a first conductivity dopent type; a secondsemiconductor layer overlying said first semiconductor layer, having asimilar conductivity type as said first layer, but a different dopentconcentration; a third semiconductor layer having a second conductivitydopent type opposite that of said first semiconductor layer, disposed inoverlying relation to said second semiconductor layer; a plurality offirst regions of said first conductivity type electrically connectingwith said first semiconductor layer, having a top element makingelectrical contact to said first regions and said first semiconductorlayer; a plurality of second regions of said second conductivity dopenttype laterally spaced from said first regions, being electricallyconnected to said third semiconductor layer having a top element makingelectrical contact to said second regions and said second semiconductorlayer. a plurality of third regions of said first semiconductor layerconductivity dopent type laterally spaced and interposed between saidsecond regions,
 13. The ESD protection structure of claim 12 whereby theplurality of first regions together with the associated connected firstsemiconductor layer are with n dopent and form multiple collectorelements of a bipolar transistor in which the bases are formed by saidthird conductivity layer and associated said plurality of second regionsof p dopent, and by which multiple emitter elements are formed by saidplurality of laterally spaced third regions of n type dopent.
 14. TheESD protection structure of claim 12 whereby said first collectorregions have horizontal contact conductor stripes at the top and bottomof said transistor array which are ultimately connected together and toa first voltage source of said integrated circuit input/output pin. 15.The ESD protection structure of claim 12 whereby said laterally spacedpluralities of third emitter regions are arranged in an alternatingarray within said third semiconductor base layer, with “N” number ofemitter regions whereby “N” corresponds to the number of multiplebipolar transistors in an electrically parallel transistor array thatcomprise said ESD protection structure.
 16. The ESD protection structureof claim 12 whereby said third semiconductor emitter regions areelectrically connected by a contact conductor element with N horizontalconductor stripe elements and further connected in a contiguousserpentine manner by vertical contact conductor elements at alternateends of said horizontal emitter stripes, and said base has horizontalcontact regions interdigitated between said horizontal emitter stripeswith the number of interdigitated horizontal base elements being equalto N+1.
 17. The ESD protection structure of claim 12 whereby saidplurality of second semiconductor base region electrical contactconductor elements and said third semiconductor emitter regionelectrical contact conductors are ultimately connected together and to asecond voltage source, typically ground.
 18. An integrated vertical npnmultiple transistor ESD protection structure on a semiconductorsubstrate, functionally connected to an integrated circuit input oroutput pin which will prevent electrostatic discharge damage to saidintegrated circuit comprising; a first semiconductor layer having afirst conductivity dopent type; a second semiconductor layer overlyingsaid first semiconductor layer, having a similar conductivity type assaid first layer, but a different dopent concentration; a thirdsemiconductor layer having a second conductivity dopent type oppositethat of said first semiconductor layer, disposed in overlying relationto said second semiconductor layer; a plurality of first regions of saidfirst conductivity type electrically connecting with said firstsemiconductor layer, having a top element making electrical contact tosaid first regions and said first semiconductor layer; a plurality ofsecond regions of said second conductivity dopent type laterally spacedfrom said first regions, being electrically connected to said thirdsemiconductor layer having a top element making electrical contact tosaid second regions and said second semiconductor layer; a plurality ofthird regions of said first semiconductor layer conductivity dopent typelaterally spaced and interposed between said second regions;
 19. The ESDprotection structure of claim 18 whereby the plurality of first regionstogether with the associated connected first semiconductor layer arewith n dopent and form multiple collector elements of a bipolartransistor in which the bases are formed by said third conductivitylayer and associated said plurality of second regions of p dopent, andby which multiple emitter elements are formed by said plurality oflaterally spaced third regions of n type dopent.
 20. The ESD protectionstructure of claim 18 whereby said first collector regions havehorizontal contact conductor stripes at the top and bottom of saidtransistor array which are ultimately connected together and to a firstvoltage source of said integrated circuit input/output pin.
 21. The ESDprotection structure of claim 18 whereby said laterally spacedpluralities of third emitter regions are arranged in an alternatingarray within said third semiconductor base layer, with “N” number ofemitter regions whereby “N” corresponds to the number of multiplebipolar transistors in an electrically parallel transistor array thatcomprise said ESD protection structure.
 22. The ESD protection structureof claim 18 whereby one said second semiconductor base horizontalcontact region lies between said top horizontal collector contact andsaid multiple emitter contact regions, and a second said semiconductorbase horizontal contact region lies between the bottom horizontalcollector contact and said multiple emitter contact regions enablingsurface connections to said base regions
 23. The ESD protectionstructure of claim 18 whereby said third semiconductor emitter regionsare electrically connected by a contact conductor element with Nhorizontal stripe elements and connected in a contiguous serpentinemanner by vertical contact conductor elements at alternate ends of saidhorizontal emitter conductor stripes.
 24. The ESD protection structureof claim 18 whereby said plurality of second semiconductor base regionelectrical contact conductor elements and said third semiconductoremitter region electrical contact conductors are ultimately connectedtogether and to a second voltage source, typically ground.
 25. Anintegrated multiple vertical npn transistor ESD protection structure ona semiconductor substrate, functionally connected between an integratedcircuit input or output pin and ground which will prevent electrostaticdischarge damage to said integrated circuit comprising; a firstsemiconductor layer having a first conductivity dopent type; a secondsemiconductor layer overlying said first semiconductor layer, having asimilar conductivity type as said first layer, but a different dopentconcentration; a third semiconductor layer having a second conductivitydopent type opposite that of said first semiconductor layer, disposed inoverlying relation to said second semiconductor layer; a plurality offirst regions of said first conductivity type electrically connectingwith said first semiconductor layer, having a top element makingelectrical contact to said first regions and said first semiconductorlayer; a plurality of second regions of said second conductivity dopenttype laterally spaced from said first regions, being electricallyconnected to said third semiconductor layer having a top element makingelectrical contact to said second regions and said second semiconductorlayer. a plurality of third regions of said first semiconductor layerconductivity dopent type laterally spaced and interposed between saidsecond regions,
 26. The ESD protection structure of claim 25 whereby theplurality of first regions together with the associated connected firstsemiconductor layer are with n dopent and form multiple collectorelements of a bipolar transistor in which the bases are formed by saidthird conductivity layer and associated said plurality of second regionsof p dopent, and by which multiple emitter elements are formed by saidplurality of laterally spaced third regions of n type dopent.
 27. TheESD protection structure of claim 25 whereby said laterally spacedpluralities of third emitter regions are arranged in an alternatingarray within said third semiconductor base layer, with “N” number ofemitter regions whereby “N” corresponds to the number of multiplebipolar transistors in an electrically parallel transistor array thatcomprise said ESD protection structure.
 28. The ESD protection structureof claim 25 whereby said first collector regions have horizontal contactconductor stripes at the top and bottom of said transistor array whichare ultimately connected together and to a first voltage source of saidintegrated circuit input/output pin.
 29. The ESD protection structure ofclaim 25 whereby said array comprises a said contact and said emittercontact region, and a said second semiconductor base horizontal contactregion between the bottom horizontal collector contact and a “N” numberof said n doped third semiconductor emitter regions whereby “N”corresponds to the number of multiple bipolar transistors in anelectrically parallel transistor array that comprise said ESD protectionstructure.
 30. The ESD protection structure of claim 25 whereby saidthird semiconductor emitter regions are electrically connected by aconductor element with N horizontal stripe conductor elements andconnected in a contiguous comb like manner by a vertical contactconductor element at one end of said horizontal emitter conductorstripes.
 31. The ESD protection structure of claim 25 whereby saidplurality of second semiconductor base region electrical contactconductor elements and said third semiconductor emitter regionelectrical contact conductors are ultimately connected together and to asecond voltage source, typically ground.
 32. An integrated verticalmultiple npn transistor ESD protection structure on a semiconductorsubstrate, functionally connected between an integrated circuit input oroutput pin and ground which will prevent electrostatic discharge damageto said integrated circuit comprising; a first semiconductor layerhaving a first conductivity dopent type; a second semiconductor layeroverlying said first semiconductor layer, having a similar conductivitytype as said first layer, but a different dopent concentration; a thirdsemiconductor layer having a second conductivity dopent type oppositethat of said first semiconductor layer, disposed in overlying relationto said second semiconductor layer; a plurality of first regions of saidfirst conductivity type electrically connecting with said firstsemiconductor layer, having a top element making electrical contact tosaid first regions and said first semiconductor layer; a plurality ofsecond regions of said second conductivity dopent type laterally spacedfrom said first regions, being electrically connected to said thirdsemiconductor layer having a top element making electrical contact tosaid second regions and said second semiconductor layer; a plurality ofthird regions of said first semiconductor layer conductivity dopent typelaterally spaced and interposed between said second regions;
 33. The ESDprotection structure of claim 32 whereby the plurality of first regionstogether with the associated connected first semiconductor layer arewith n dopent and form multiple collector elements of a bipolartransistor in which the bases are formed by said third conductivitylayer and associated said plurality of second regions of p dopent, andby which multiple emitter elements are formed by said plurality oflaterally spaced third regions of n type dopent.
 34. The ESD protectionstructure of claim 32 whereby said laterally spaced pluralities of thirdemitter regions are arranged in an alternating array within said thirdsemiconductor base layer, with “N” number of emitter regions whereby “N”corresponds to the number of multiple bipolar transistors in anelectrically parallel transistor array that comprise said ESD protectionstructure.
 35. The ESD protection structure of claim 32 whereby saidfirst collector regions have horizontal contact conductor stripes at thetop and bottom of said transistor array which are ultimately connectedtogether and to a first voltage source of said integrated circuitinput/output pin.
 36. The ESD protection structure of claim 32 wherebysaid array comprises a said second semiconductor base horizontal contactregion between the said top horizontal collector contact and saidemitter contact region, and a said second semiconductor base horizontalcontact region between the bottom horizontal collector contact and a “N”number of said n doped third semiconductor emitter regions whereby “N”corresponds to the number of multiple bipolar transistors in anelectrically parallel transistor array that comprise said ESD protectionstructure.
 37. The ESD protection structure of claim 32 whereby saidthird semiconductor emitter regions are electrically connected by aconductor element with N horizontal stripe conductor elements andconnected in a contiguous box like manner by vertical contact conductorelements at both ends of said horizontal emitter conductor stripes. 38.The ESD protection structure of claim 32 whereby said plurality ofsecond semiconductor base region electrical contact conductor elementsand said third semiconductor emitter region electrical contactconductors are ultimately connected together and to a second voltagesource, typically ground.
 39. A Method for forming an integratedmultiple transistor ESD protection device on a semiconductor substrate,functionally connected to an integrated circuit input or output pinwhich will prevent electrostatic discharge damage to said integratedcircuit comprising; forming a first semiconductor layer having a firstconductivity dopent type; forming a second semiconductor layer overlyingsaid first semiconductor layer, having a similar conductivity type assaid first layer, but a different dopent concentration; depositing athird semiconductor layer having a second conductivity dopent typeopposite that of said first semiconductor layer, disposed in overlyingrelation to said second semiconductor layer; forming a plurality offirst regions of said first conductivity type electrically connectingwith said first semiconductor layer, having a top element makingelectrical contact to said first regions and said first semiconductorlayer; forming a plurality of second regions of said second conductivitydopent type laterally spaced from said first regions, being electricallyconnected to said third semiconductor layer having a top element makingelectrical contact to said second regions and said second semiconductorlayer; forming a plurality of third regions of said first semiconductorlayer conductivity dopent type laterally spaced and interposed betweensaid second regions; and having a top element of conducting materialmaking electrical contact external to said third regions;
 40. The methodaccording to claim 39 whereby said first semiconductor layer is formedof a heavily doped n+ material from either an arsenic or antimony ionimplant process with an energy range of between about 25 and 30 KeV witha dosage of between about 10¹⁴ and 10¹⁵ a/cm² to produce a buried layerdopent concentration between 10¹⁸ and 10¹⁹ a/cm³.
 41. The methodaccording to claim 39 whereby said semiconductor layer is a deposited nepitaxial layer doped with arsenic to produce a concentration of 10¹⁵and 10¹⁶ a/cm³.
 42. The method according to claim 39 whereby saidplurality of first regions are n+ semiconductor material created witheither an arsenic or antimony ion implant with an energy range, ofbetween about 25 and 30 KeV with a dosage of between about 10¹⁴ and 10¹⁵a/cm² to produce a dopent concentration between 10¹⁸ and 10¹⁹ a/cm³ toform the collector contact regions.
 43. The method according to claim 39whereby said third semiconductor layer is a p layer bipolar base regioncreated by an ion implant using boron as a dopent with an energy rangeof about 30 KeV with a dosage level of about 10¹² a/cm² to produce aresultant concentration of about 10¹⁸ a/cm³.
 44. The method according toclaim 39 whereby said second plurality of regions are p+ base contactregions formed from using boron in an ion implant with a dosage level ofbetween 10¹³ and 10¹⁴ a/cm² to create a doping concentration of between10¹⁸ and 10²⁰ a/cm³.
 45. The method according to claim 39 whereby saidthird regions are n doped multiple emitter regions formed using aphosphorus ion implant with an energy range of about 30 KeV and with adosage level of between 10¹⁶ and 10¹⁷ a/cm² to create a dopingconcentration of 10¹⁹ and 10²⁰ a/cm³.
 46. The method according to claim39 whereby said collector electrical contacts are connected by eitherpolysilicon or aluminum conductor elements to said integrated circuitsinput or output pins, and said base and emitter electrical contacts areelectrically connected together by either polysilicon or aluminumconductor elements and connected to a second voltage source, typicallyground.